Clostridium difficile infection is associated with consumption of antibiotics which disrupt the normal microbial flora of the gut, allowing Clostridium difficile to establish itself and produce disease. Currently, only vancomycin or metronidazole is recommended for treatment and many patients suffer from relapse on infection (Expert Opin. Ther. Patents (2010) 20(10), pp. 1389-1399).
EP2177214 A1 describes use of ozenoxacin for Clostridium difficile. 
Some quinolone compounds useful as antibacterial agents are disclosed in JP1-319463 A, WO99/51588, WO99/03465, JP3-66301 B and WO99/07682.